Abstract:Extreme climate events pose dual challenges to the timeliness and reliability of decision-making in winter wheat production. Effective decision-making requires not only support from domain-specific agricultural knowledge but also quantitative assessment of continuous processes such as crop phenological development. Although general-purpose large language models (LLMs) have demonstrated considerable potential for decision support, their application remains constrained by insufficient coverage of domain knowledge, limited robustness in numerical reasoning, and inadequate traceability in complex decision-making processes. To address these limitations, integrateing graph retrieval-augmented generation (GraphRAG) with the crop model (CropGrow) to develop an intelligent decision-support agent for winter wheat production under extreme climate events. The agent employed an agricultural knowledge graph as its evidence base and encapsulates CropGrow as a numerical computation service through the model context protocol (MCP). A coordination module orchestrated query interpretation, evidence retrieval, crop model invocation, and result validation, thereby enabling knowledge-based evidence and process-based mechanistic computation to operate synergistically within a unified decision-making workflow. Evaluation using 450 extreme-climate question-answer pairs and 111 sets of field-observed phenological data showed that, compared with the same backbone model, Qwen3-Max, the expert-weighted recall of core entities was increased from 30.69% to 37.15%, while the density of unsupported risk-related statements was decreased from 8.63 to 5.49 per 1 000 words. After integrating CropGrow, the root mean square error (RMSE) for flowering and maturity date predictions was decreased from 20.88 days to 5.79 days, while the coefficient of determination (R2) was increased from 0.027 to 0.896. Overall, the coordinated orchestration of the proposed agent improved both domain knowledge coverage and phenological prediction performance under extreme climate disaster scenarios, providing a feasible technical framework for the rapid formulation of disaster-response strategies in winter wheat production.